Multiple *.adml, *.opal files, why??

I downloaded and extracted the latest Office 2016/2019 admx files and corresponding adml files and opax/opal files.

I observed that now instead of one adml file, there's multiple numbered adml files. Same for the Office opal files.

e.g. access16.opal, access16.opal0, access16.opal1, access16.opal2, up to .opal9

e.g. access16.adml, access16.adml0, access16.adml1, access16.adml2, up to .adml9

Why is this?? What does this mean?? I assume all the adml files, numbered or not, should be put into the central store.

Also, where are opax/opal files installed??

Thank you, Tom